TIPS WITH TONY: New Silicone Rubber Materials

We’ve expanded our selection of liquid silicone rubber (LSR) materials, which have some distinct elastic and optical advantages over certain thermoplastics. In addition to three durometers of general-use Elastosil LSR, and medical- and optical-grade Dow Corning materials, we now have two new durometers of Elastosil and a fuel-resistant flourosilicone material at Proto Labs.

Elastosil LSR
Elastosil LSR is a great general-use material that has good moldability characteristics, a good overall appearance and is transparent until colorant is added. Shore A durometers of 40 and 60 have been added our current offering of 30, 50, and 70 durometers.

Technical specs:

  • 40 durometer Elastosil has a tensile strength of 10.0 N/mm² with a tear strength of 33 N/mm and an elongation break of 610%.
  • 60 durometer Elastosil has a tensile strength of 9.40 N/mm² with a tear strength of 27 N/mm and an elongation break of 340%.

THE SHORT LIST: 5 Med-Friendly Materials

Developing medical devices or health care components? Here’s five good material options to consider.

PEEK, PEI (Ultem) and PPSU (Radel). Attributes: High temperature resistance, creep resistance and works well for applications that require sterilization.

Polycarbonates (Makrolon and LEXAN HP1). Attributes: Good clarity with clear and translucent applications, good impact resistant, and durability.

Medical-grade LSR.

Medical-grade liquid silicone rubber (QP1-250). Attributes: Thermal, electrical and chemical resistance, biocompatibility, and is suitable for skin contact.

Titanium (Ti 6-4). Attributes: Lightweight, temperature and corrosion resistant 3D printed metal used with direct metal laser sintering (DMLS) process to produce fully functional medical components.

WaterShed XC 11122.

WaterShed XC 11122. Attributes: ABS-like material used to 3D print clear microfluidic parts with sterolithography (SL) process. Resistance to water and humidity, and good for lens and flow-visualization models.

For more information on materials, check out our complete selection at protolabs.com, and to learn more about using rapid manufacturing to develop health care and medical products, read our white paper: Prototyping and Low-Volume Production for Medical Applications.

Finding the Right Surface Finish

Molded parts are everywhere — from highly cosmetic housings hiding in plain sight to internal components where a fine polish is unnecessary. Most people pay no attention to the surface finish on those parts, but for product designers and engineers, it’s an important design consideration.

Identifying the right surface finish is dependent on a few important elements, namely the development or production stage that your parts are in, the materials they’re being manufactured in and their end-use applications.

On custom finishes, use color coding to provide a clearly marked image of your CAD model with its required finishes.

This month’s tip discusses:

  • available surface finishes for injection molded parts at Proto Labs
  • how to create a custom surface finish involving two or more finishes
  • navigating finishes within ProtoQuote
  • why gating and ejection play a limited role in liquid silicone rubber parts
  • secondary options applied to magnesium components

Read the full design tip here.

TIPS WITH TONY: LSR Offers Design Flexibility

There are many reasons why you should be looking at liquid silicone rubber (LSR) — I’ll highlight a few big ones in order to get you thinking about this versatile thermoset.

For a deeper dive into LSR and how it’s used in the lighting industry, please attend my free tech talk webinar hosted by Tech Briefs.

LSR Molding
LSR parts are formed in process similar to that of conventional plastic injection molding with one main difference. LSR is a thermoset material that compounds two liquids together, which is then heat cured in the mold to produce a part. The material delivery system is cooled and only the mold is heated. This is unlike thermoplastic molding, which begins with the melting of plastic pellets that are injected into a heated mold.

Optical LSR is highly flexible and can replace glass in many lighting applications.

LSR Advantages
LSR parts are strong, elastic, chemical resistant, serializable and biocompatible, and have a range of operating temperatures. The benefits of LSR lend itself well to the automotive, medical and lighting industries where gaskets, seals and lighting lenses are frequently used.

LSR parts have a very good temperature resistance, ranging between -49°F to 392°F; they are non-yellowing, UV stable and optical LSR has up to 94 percent light transmission; they offer good vibration control and offer up to 400 percent flexibility along with excellent part memory.

The chart pretty much speaks for itself when comparing LSR to PC, PMMA and glass when looking at replacing the traditional materials with LSR.

Design Flexibility
Traditional thinking of part design needs to be considered, but many can be broken:

  • Part thicknesses greater than 1 in. and less than 0.020 in. are achievable with little to no concern of any unsightly sinks or internal voids.
  • No ejector pins are used to remove parts from the mold as they are all hand-removed.
  • Gates are nearly invisible, barely thicker than flash. LSR flows like water, so the gate needs to be very shallow, but wide.
  • Negative draft angles or increased undercuts are a possibility with up to 400 percent part flexibility and part memory.
  • Ability to fill fine details or voids.
  • Ability to combine components reducing number of parts to assemble, e.g., combining a lens and seal for lighting applications.

For more information on LSR, please download our white paper or listen in to my tech talk presentation mentioned at the top of the tip. You can also visit our website at protolabs.com or contact one of our customer service engineers at customerservice@protolabs.com or 877.479.3680 with additional questions on any of our services.

LSR Molding Gets Medical-Grade Silicone, Increases Size Envelope

The medical industry continues to grow and change, and Proto Labs is working to stay ahead of the curve with our capabilities by making some significant enhancements to our Liquid Silicone Rubber (LSR) molding process. The most recent updates include the addition of medical-grade QP1-250 LSR to our material options and the ability to produce larger LSR parts. Continue reading